In two places that I've worked, the pendulum swung quite far in the other direction -- 20% time was instituted because the people whose roles involved creating a product vision (business development, management, etc.) were unable to introduce successful changes. Not only would the company leadership rally behind any promising output from 20% time, they were practically counting on it, putting additional responsibility on the developers without any additional reward -- and naturally, the stagnant creative/leadership roles would subsume a successful project.

To any managers/leaders out there thinking of instituting 20% time: please, please don't do it if it's a last-ditch effort to innovate. Your employees may put up with it if they value job security, but they can tell that the resulting power dynamics within the organization are unfavorable to them.